Sensors or electronic inserts are filled with the most varied of potting compounds in the electronics- or final manufacture for different reasons, such as e.g. protection against moisture or explosion protection. In such case, the potting compound is, in most cases, cast with the assistance of the force of gravity under usual atmospheric conditions from above into housing openings. In such case, the material flows relatively without control around the electronic parts present in the housing and finds its paths for itself. Air inclusions and bubble formation cannot always be excluded using this method, so that different approaches are used for preventing the bubbles and air inclusions. Examples include filling under vacuum, long cure times after potting (bubbles should rise), stepwise casting (with interspersed quiet times), vibrating the potting compound, and filling under pressure.
The described methods often deliver non-reproducible results or do not permit high working speeds, since back pressure can occur from bottlenecks in the housing or air cannot sufficiently escape in the case of narrow filling locations. If additional measures are applied, higher costs of the product result.
DE 102008043169 A1 describes an apparatus with a housing, which has an opening. The housing includes a first housing section, in which a sensor electronics is arranged. An insert is inserted into the first housing section, wherein the insert comprises a tubular, basic body. A filling tube is introduced into the insert and serves to fill the insert with a first potting compound. The filling tube introduced into the insert enables a filling of the potting compound into the insert, without giving rise to air inclusions.
Disadvantageous in the case of the application of a filling tube is that, for space reasons a, most often, very small diameter of the filling tube must be used. The small opening requires performing the filling under pressure, in order to be able to assure a sufficient filling speed. The junction between filling tube and potting machine must be appropriately shape-interlocked, which requires a very precise orientation of a fill needle. Further disadvantageous in the case of such a filling tube is that, after the filling of the housing with potting compound, it remains in the housing, since a withdrawal of the filling tube from the potting compound would introduce more air into the potting compound.